A. Field of the Invention
The present invention relates generally to power cords for electrically connecting an object to an electrical outlet. In particular, the present invention relates to such power cords that are utilized to electrically connect an electric dryer to an electrical outlet. Even more particularly, this invention relates to such power cords which can selectively connect to an electrical outlet having a receptacle with either a four-prong or three-prong configuration.
B. Background
For many years, a large percentage of the population in the United States has primarily used electrically powered dryers for drying clothes, bedding, shoes and other materials. A power cord connects the electric dryer to a source of electrical power, which is typically a wall mounted electrical outlet. Because of the higher electrical load requirements, electric dryers have historically utilized a power cord having a specially configured three-prong plug that is received into a cooperatively configured three-prong receptacle. As a result, most older homes were built with an electrical outlet having a three-prong receptacle in the area where the electric dryer was placed. Since approximately 1996, however, nearly all municipal electrical codes require four-prong receptacles at the electrical outlet to which the dryer connects and use of a cooperatively configured four-prong plug for the electric dryer power cord. In addition to the black and red power wires and the white neutral wire, the four-prong power cord has a green ground wire that does not carry any current. Instead, the green ground wire is grounded back to the junction box or to a separate ground. Inside the dryer, the white neutral wire is not bonded to the chassis and the green wire is grounded from the wiring terminals.
Most homes built prior to 1996 have the three-prong receptacle for the electric dryer, which will not work with the four-prong plugs that are required for newer dryers. Because so many older homes have a three-prong receptacle, most municipal codes allow the dryer to be rewired for use with a power cord that has a three-prong plug. Rewiring the electric dryer involves disconnecting the separate ground strap and connecting it to the neutral white wire, which in effect reverts the dryer wiring arrangement to the pre-1996 configuration. As a result, most dryer manufactures configure their dryers to work with either a three-prong or a four-prong power cord. Typically, this requires the manufacturer or retailer to deliver the dryer to the home with both of these power cords and then rewire the dryer at the purchaser's home for use with either a three-prong receptacle or a four-prong receptacle, depending which is utilized in the home. Having to provide two power cords increases the cost of the dryer, increases inventory issues with regard to keeping both types of power cords in stock and increases the time and cost to deliver and set-up the dryer. Although the home itself could be rewired to replace an existing three-prong receptacle with a four-prong receptacle, most homeowners do not want to incur the expense for such rewiring.
What is needed, therefore, is an improved power cord that allows the user to electrically connect an electric dryer to an outlet having a receptacle with either four prong-receiving openings or three prong-receiving openings. The preferred power cord should be configured to allow a user to quickly and without any rewiring of the dryer or the outlet selectively connect the power cord to either a four-prong opening receptacle or a three-prong opening receptacle, whichever is already present at the home or other place of delivery. The power cord should be configured to safely interconnect the dryer to the outlet so the user will not be exposed to the risk of an electrical shock.